In most cases, machines and components used in performing industrial processes receive power from public utility companies. Unfortunately, power supplied by utility companies is often subject to transient reductions in voltage level (sags) or increases in voltage level (swells). These sags and swells can have deleterious effects on sensitive industrial processes.
Sag/swell generators are devices that are typically placed in the power circuit between a power supply and a load to introduce controlled and repeatable voltage sags or swells. Using these generators, engineers can perform tests to observe the effects of voltage sags and swells on industrial machines and processes. Using information gathered during such tests, the engineers can determine ways to adjust the machines and processes to minimize harmful effects of voltage variations.
The usefulness of prior voltage sag/swell generators has been limited because they have not provided test engineers the ability to easily select between different modes of generating a voltage sag or swell using a single generator. For example, if a test engineer wished to do a first test wherein a voltage sag in a three-phase power system is described by a reduction in amplitude of a single phase-to-neutral voltage (simulating a line-to-ground fault on the utility system), and then do a second test wherein the sag is described by a phase-to-phase reduction (simulating two overhead distribution lines coming into contact with one another), those tests would have to be performed using different sag generators. This is inconvenient due to the time and effort involved in setting up two different generators. The cost in providing two sag generators can also be significant.
What is needed, therefore, is a sag/swell generator having multiple modes of operation whereby the amplitude and phase relationships of each phase in a three-phase system is selectable by the test personnel.